On Mon, Jul 02, 2012 at 10:18:43AM +0200, Takashi Iwai wrote: > At Thu, 28 Jun 2012 14:23:04 -0400, > Giacomo Comes wrote: > > > > On Thu, Jun 28, 2012 at 07:52:18AM +0200, Takashi Iwai wrote: > > > At Tue, 26 Jun 2012 15:08:32 -0400, > > > Giacomo Comes wrote: > > > > > > > > I have a dell latitude E6420 with Sandybridge Mobile (GT2). > > > > Since I got it (about one year ago), it has been a nightmare to run linux on it. > > > > At the beginning I installed openSUSE 11.4 (kernel 2.6.37.6) and the laptop > > > > would freeze almost immediately. After that I waited for newer kernels in order to > > > > see if things would improve. They did improve indeed and finally with kernel 3.0 > > > > I was able to run linux (openSUSE 11.4) without laptop freeze or screen issue. > > > > Unfortunately, the only kernel that works with my laptop is 3.0. Newer kernel > > > > (3.1, 3.2, 3.3 and 3.4) do not work. > > > > This is what happen if I run kernel 2.6.39, 3.1, 3.2, 3.3 and 3.4: > > > > The laptop boot and does the boot process fine. At the end of the boot process X > > > > starts and here the problem appears (about 50% of the times): > > > > the screen goes black on the left side (about 2/3 of the whole screen) with white > > > > stripes to the right side (the remaining 1/3). > > > > The laptop is not dead: I can remotely login or I can perform a clean shutdown > > > > if I press the power button, but the screen is totally dead. > > > > Another strange issue is that after a bad boot (with the black screen) at the > > > > next reboot the screen will start to flicker. The flickering will last some time > > > > and it will become less intense as the time goes until it will disappear completely. > > > > The funny thing is that the intensity of flicker depends on how long I keep the > > > > black screen. If, after the boot process, the black screen appears and I reboot > > > > the laptop immediately, then the flicked is moderate and it disappear after > > > > 1 or 2 minutes. If I keep the black screen for 1 minute or more, then after the > > > > reboot the flicker is very intense and it takes much more to fade. > > > > > > This reminds me of a similar bug I've seen on HP laptops with HD+ > > > (1600x900) monitors. Could you check whether the patch below helps? > > > > > > Note that it just avoids entering to the wrong mode. If your laptop > > > already starts flickering, at first recover from the flickering state, > > > apply the patch, and reboot/test. > > > > > > > > > Takashi > > > > > > --- > > > diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c > > > index 08eb04c..3f61bba 100644 > > > --- a/drivers/gpu/drm/i915/intel_lvds.c > > > +++ b/drivers/gpu/drm/i915/intel_lvds.c > > > @@ -413,7 +413,7 @@ static void intel_lvds_prepare(struct drm_encoder *encoder) > > > * the panel fitter. However at all other times we can just reset > > > * the registers regardless. > > > */ > > > - if (!HAS_PCH_SPLIT(encoder->dev) && intel_lvds->pfit_dirty) > > > + /*if (!HAS_PCH_SPLIT(encoder->dev) && intel_lvds->pfit_dirty)*/ > > > intel_lvds_disable(intel_lvds); > > > } > > > > > > > This patch seems to fix the problem. I will regularly run a kernel with > > this patch and report if I see any other issue. > > Which native resolution does your machine have? > If it's 1600x900 or such, we may consider to apply the workaround > generically for such resolutions. AFAIK, all the HP machines affected > by this symptom have 1600x900 panels (but different panel vendors). My laptop's resolution is 1600x900. If it may help I will describe more in details how the bug appears: it can be in two different moments, one is when X starts, sometime the screen goes black sometimes it stays ok. When it stays ok, it is possible to work without issue, but on logout, when X is stopped, sometime the screen will become black and sometime it will stay ok. So the screen issue appears when X starts or when X stops. Giacomo
